The construction of dwellings utilizing logs stacked upon one another is popularly practised in regions where timber is available. Hand-held chainsaws have proven to be well-suited for carrying out the rough cutting operations required in this type of construction, such as the felling of trees and cutting is of same to length, and are widely used therefor. However, it is also necessary that openings be provided in stacked-log structures, so as to enable the insertion of doors or windows therein. Hand-held chainsaws are known to have been used for these purposes, but it has proven difficult for hand-held chainsaws to be manually-directed with the necessary level of precision required to produce aesthetically-pleasing openings within which doors or windows may be readily inserted and mounted. Moreover, even for highly-skilled chainsaw operators, handling mishaps are inevitable, which can require the costly replacement of timber, and also hold the potential of causing serious injury to the operator of the chainsaw and/or to bystanders.
Chainsaw guides are known in the art, particularly for use in the processing of logs into dimensional lumber, such as that disclosed in U.S. Pat. No. 4,476,759 (Aderneck), issued Oct. 16, 1984. The Aderneck patent discloses a chainsaw guide attachment comprising a rigid guide channel, a threaded cylinder attached to the guide channel, a threaded shaft mechanically engaged within the threaded cylinder, and a clamp attached to the threaded shaft and adapted to grip a conventional hand-held chainsaw. The clamp comprises twin set screws and a hardened backing plate between which the cutting bar of the chainsaw may be positioned. In preparation for use, the operator is required only to clamp the attachment to the chainsaw by manipulation of the set screws against the cutting blade, and fasten a guide rail, such as a common 2".times.4" wooden stud, to the log. Thereafter, the guide channel may be fitted upon the guide rail, and the chainsaw be caused to cut the log by pivotal rotation of the threaded shaft in the threaded cylinder; once such pivotal rotation is completed, the guide channel may be repositioned on the guide rail, and the process repeated along the entire length to be cut.
The twin set screws and hardened backing plate of the Aderneck attachment which effect the gripping of the chainsaw have been known to cause damage to chainsaw guide bars in use, but otherwise, attachments of this type have generally proven useful for the rough-cutting of logs into dimensional lumber, such as is required for framing purposes. However, the Aderneck attachment suffers in several aspects when employed in the provision of openings in stacked log structures. Firstly, due to the utilisation of the threaded shaft and cylinder pivot assembly in the Aderneck attachment, the displacement of the chainsaw relative to the guide channel varies during rotation of the chainsaw. This variance results in lateral movement of the chainsaw blade during cutting, thereby producing a contoured cut surface which is poorly suited for the mounting of door or window frames thereupon and which may require subsequent shimming, sanding or planing. Moreover, the cut edge produced is jagged and aesthetically unpleasing. As well, as conventional chainsaws are not adapted for lateral blade movement, the aforementioned variance results in unnecessarily high levels of operator effort being required to effect pivotal rotation, which is further accentuated by the frictional forces resident in the pivot assembly itself, and by the absence of means to retain the chainsaw against the structure; the requirement that the operator physically support the chainsaw and guide attachment during operation, coupled with the high effort levels required to effect pivotal rotation of the chainsaw during operation, results in high levels of operator fatigue, leading to handling mishaps, property damage and operator injury.